The present device relates to a sensor capable of detecting changes in the electromagnetic field it generates when in proximity to either conductive or nonconductive materials and a device for orbiting about the joint between two tubular components for inspecting the welded or joined joint.
There has been a persistent need to inspect both conductive and nonconductive items for consistency and for the presence of flaws with a single technology capable of overcoming deficiencies associated with traditional x-ray, eddy current, ultrasonic and other nondestructive inspection methods currently employed. The problem with x-ray has been the dangerous nature of the high energy electromagnetic wave and the hazards to biological organisms are well understood, given this and the need for elaborate shielding, x-ray can be very undesirable. Also, while x-ray is useful for detecting volumetric anomalies such as voids or the presence of foreign objects, flaws such as cracks where the adjoining faces of the cracks may be in intimate contact and having no appreciable volume, are very difficult to detect.
Standard eddy current inspection is useful in detecting discontinuities in metal and other conductive materials, but do not work well when inspecting nonconductive materials. The inability to inspect nonconductive materials has limited eddy current applications. Eddy current inspection may also employ design features which allow the effects of signal output due to changes in liftoff (the distance between the sensor and the item) to be inspected to be mitigated. These design features are permanent and may not be changed on the fly during inspection, thus limiting its ability to instantaneously determine liftoff.
Ultrasonic inspection can be difficult to employ, given the need to provide a coupling fluid or gel to transmit the ultrasonic frequency from a transducer to a target being inspected. It is often impractical to use such coupling fluids and gels on many structures as well as completed structures such as can be expected in the air frame of a finished aircraft, especially when constructed of composite. Also, it is not possible to use ultrasonic inspection technologies when there is an air gap separating otherwise inspectable walls, as air lacks the necessary transmissive qualities associated with a coupling fluid.
Furthermore, the problem of inspecting small orbitally welded systems comprised of at least two components, each having at least one tubular extension meant to convey fluid with the extensions being orbitally welded one to the other, has been one of accessibility and motion control. Orbitally welded assemblies are generally comprised of at least two components, each component having at least one tubular element extending from the component for conveying fluid. The tubular elements of at least two components are connected one to the other by way of orbital welding such as the orbital welding method described in McGushion U.S. Pat. No. 5,196,664.
Motion control is required to precisely place a sensing means over a weld joint and move the sensing means rotatably, and at times translationally, around the central axis of the weld joint in order to accomplish a complete inspection of the joint, areas adjacent to the joint, and areas in transition with the joint (known as the heat affected zone) in the smallest envelope possible.
To inspect the above type of joint, a motion control system must also be able to transport a sensing means around a joint while avoiding impact or other mechanical interference with other components in the orbitally welded assembly. Orbitally welded components are often in close proximity to the joint being inspected as might be expected in the tight confines of a propulsion system of a satellite, rocket, or the hydraulic system of a fighter or commercial jet. In these tight applications, densely configured fluid control systems are often made with the prerequisite need to economize both size and weight. It is also necessary to transmit the data collected with such an inspection means to a computer controlled processing means and graphical interface so that the sensing means signal output may be correlated to a precise location on the welded joint in graphical form which can then be easily interpreted.
Previous attempts to image these sorts of orbital welds have almost exclusively been done with an x-ray means, either with the use of film, computer tomography (CT), digital real-time radiography (digital RTR). The use of x-rays creates a safety hazard, where the work area must be evacuated and lead shielding employed. While x-ray inspection is well suited to discovering volumetric flaws such as porosity or inclusions of foreign objects in the weld, they are ill suited for discovering flaws, such as cracks which have very little volume. Additionally, x-ray inspection is time consuming, often requiring the orbital weld assembly to be removed from manufacture and brought to an x-ray booth. X-ray inspection often requires secondary methods to be used in order to effectively detect cracks which may not have been otherwise visible. The secondary method of inspection is generally a dye penetrant inspection, where fluorescing liquid is applied to the surface of the weld causing any existing surface cracks or imperfections to be filled with minute quantities of the liquid, which when illuminated by a type of light source, reveals the surface cracks or imperfections. The penetrant method requires a time consuming post inspection cleaning to remove the liquid. For these reasons, both x-ray and dye penetrant are inadequate to the task.
Other inspection technologies, such as eddy current sensors, eddy current sensor arrays, ultrasonic sensors, ultrasonic sensor arrays, and thermographic inspection, are capable of inspecting orbitally welded joints for evidence of surface and subsurface defects, and possess the necessary miniaturization of the sensor technology itself to inspect tightly configured orbital welds. However, each of the above inspection methods lack the combination of sufficient miniaturization and sophistication in motion control, to transport the sensor precisely and repeatedly in order to inspect a weld in the confined space of a fluid assembly that has been orbitally welded.
Accordingly, there is a need for a sensor which does not produce harmful radiation, which can inspect conductors and nonconductors alike and can inspect through walls of various materials and air gap transitions. Such a sensor should be very compact to allow easy access to confined spaces and should also allow for inspection of small features and anomalies which may be critical to the performance of the item or system being inspected. The sensor should provide an output that has signal variation relative to varying features or anomalies of a target and which may be located in the item being inspected. The sensor should have the ability to control for variables such as liftoff or material changes without the need to make permanent physical changes to the sensor.
Furthermore, there is a need for a system with a sensing means capable of inspecting cracks, volumetric flaws and other defects on and in orbital tube welds which can be rotatably transported around the central axis of a weld joint and adjacent areas, so that a complete analysis of the weld area may be made, revealing defects and cracks. Additionally, a motion control system capable of transporting a sensing means is needed, that is suitably compact to allow placement and use in areas of tight configuration within an orbitally welded assembly, where other components of that assembly may be present and in close proximity to the area being inspected. This motion control system must lend itself to rapid installation onto and removal from the joint being inspected. Such a system must also communicate its sensing means output or data to a computerized controller for graphical presentation and interpretation of data.